Xantphos as cis- and trans-chelating ligand in square-planar platinum(II) complexes. Hydroformylation of styrene with platinum-xantphos-tin(II)chloride system

Article abstract of DOI:10.1016/j.jorganchem.2003.10.045

Platinum(II) complexes of a diphosphine ligand xantphos (4,5-bis (diphenylphosphino)-9,9-dimethyl-xanthene) have been synthesised and characterised by NMR, conductivity and catalytic investigations. In addition to the parent complex cis -PtCl₂(xantphos), trans -platinum(II) complexes of square-planar geometry containing xantphos as a trans -chelating ligand can be obtained due to the large bite angle of the ligand. The platinum- xantphos -tin(II)chloride system acts as active hydroformylation catalyst in the hydroformylation of styrene resulting in high chemo- and regio-selectivities of up to 99.8% and 88%, respectively.

Full text of DOI:10.1016/j.jorganchem.2003.10.045

Journal of Organometallic Chemistry 689 (2004) 1188–1193
www.elsevier.com/locate/jorganchem
Xantphos as cis- and trans-chelating ligand
in square-planar platinum(II) complexes. Hydroformylation
of styrene with platinum–xantphos–tin(II)chloride system
a
Gyorgy Petocz , Zoltan Berente , Tamas Kegl , Laszlo Kollar
b,d
c
a,d,
*
€
€
ꢀ
ꢀ
ꢀ
ꢀ ꢀ
ꢀ
a
Department of Inorganic Chemistry, University of Pꢀecs, Ifjusag u. 6, P.O. Box 266, H-7624 Pꢀecs, Hungary
b
Institute of Biochemistry, University of Pꢀecs, P.O. Box 99, H-7643 Pꢀecs, Hungary
c
Research Group for Petrochemistry of the Hungarian Academy of Sciences, H-8201 Veszprꢀem, Hungary
d
Research Group for Chemical Sensors of the Hungarian Academy of Sciences, P.O. Box 266, H-7624 Pꢀecs, Hungary
Received 19 September 2003; accepted 31 October 2003
Abstract
Platinum(II) complexes of a diphosphine ligand xantphos (4,5-bis(diphenylphosphino)-9,9-dimethyl-xanthene) have been syn-
thesised and characterised by NMR, conductivity and catalytic investigations. In addition to the parent complex cis-PtCl2(xant-
phos), trans-platinum(II) complexes of square-planar geometry containing xantphos as a trans-chelating ligand can be obtained due
to the large bite angle of the ligand. The platinum–xantphos–tin(II)chloride system acts as active hydroformylation catalyst in the
hydroformylation of styrene resulting in high chemo- and regio-selectivities of up to 99.8% and 88%, respectively.
Ó 2004 Elsevier B.V. All rights reserved.
Keywords: Platinum; Phosphine; Trigonal bipyramidal geometry; Hydroformylation
1. Introduction
their C2 symmetry (Ôhomobidentate ligandsÕ) and the
minority of the bidentate ligands are mostly P, N or
P, O donor ligands (Ôheterobidentate ligandsÕ). The
common feature of these ligands is their coordination in
a cis-manner.
The importance of carbonylation reactions has initi-
ated many investigations [1]. Efforts have been made to
exploit enantioselective carbonylation reactions, espe-
cially hydroformylation, in the synthesis of practically
important derivatives [2].
Hundreds of ligands (among them chiral ligands)
with different steric and electronic properties, shapes
and functionalities have already been tested also in
hydroformylation [3]. The fine tuning of the electronic
and steric properties of the ligands [4], the understand-
ing of their organometallic chemistry has evolved ligand
(and consequently catalyst) development from trial and
error into rational design.
Recently, emphasis has been put on the synthesis of
ligands with specific geometries. It has been found that
bidentate ligands can have a preference for a specific
geometry, since the bite angle, defined as donor
atom(1)–metal–donor atom(2) angle, is dependent on
the bridge between the two donor atoms. The majority
of the ligands applicated up to now prefer the donor
atom–metal–donor atom bite angle close to 90° (typi-
cally between 85° and 95°), so square-planar rather than
tetrahedral geometry is favoured from sterical reasons.
Van Leeuwen et al. [5] has done a seminal work on the
systematic investigation of the influence of the larger
bite angle ligands to complex geometry. The xantphos
ligand family, enforcing bite angles between 100° and
120°, tends to occupy the bisequatorial position rather
than an axial–equatorial position in trigonal pyramidal
Most of the frequently used ligands possess two
chemically equivalent phosphorus donor atoms due to
* Corresponding author. Tel.: +36-72-327622/4153; fax: +36-72-
501527.
ꢀ
E-mail address: kollar@ttk.pte.hu (L. Kollar).
0022-328X/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2003.10.045

G. Pet€ocz et al. / Journal of Organometallic Chemistry 689 (2004) 1188–1193
1189
Rh(I) complexes. The first examples for the trans-che-
lating coordination of xantphos in Pd(xantphos)(Me)Cl
and Pd(xantphos)(4-cyanophenyl)Br complexes has been
published quite recently [6].
system for the hydroformylation of styrene will also be
presented.
To the best of our knowledge, there is a very few
examples for the use of platinum-xantphos hydro-
formylation catalyst. After the selective isomerization of
methyl 3-pentenoate to methyl 4-pentenoate remarkable
linear selectivity has been obtained [7]. On the basis of
NMR spectroscopy study the cis-coordination mode for
xantphos has been proposed in all active platinum-
xantphos species [8].
In this paper we describe the synthesis and charac-
terisation of some novel platinum complexes of xantphos
(1), the parent ligand of the series (Scheme 1). Examples
for its versatile coordination modes in platinum(II)
complexes, such as cis- and trans-chelating coordination,
as well as monodentate coordination in square-planar
platinum(II) complexes will be shown by NMR investi-
gations. The application of platinum–1–tin(II)chloride
2. Results and discussion
2.1. Synthesis and NMR characterisation of the plati-
num–xantphos complexes
Xantphos (4,5-bis(diphenylphosphino)-9,9-dimethyl-
xanthene, 1) was reacted with PtCl2(PhCN)2 in refluxing
benzene resulting in cis-PtCl2(xantphos) (1a) (Scheme 1).
The 31P NMR spectrum of 1a shows characteristic 1/4/1
pattern consisting of a doublet assigned to the two
equivalent phosphorus coupled with 195Pt (I ¼ 1=2,
natural abundance 33.8%) (appearing as a Ôplatinum
satelliteÕ) and a singlet due to those phosphorus coupled
with platinum nuclei other than 195Pt (appearing as a
Ôcentral lineÕ). The 1J(31P, 195Pt) coupling constant of
about 3693 Hz clearly indicates the presence of the
chloro ligands trans to phosphorus, i.e. the cis-chelation
of 1 (Table 1).
Cl
P
P
Pt
In dichloromethane and chloroform one of the two
Pt–Cl bonds of 1a inserts tin(II)chloride yielding two
unexpectedly broad signals at 15.5 and 5.4 ppm. Al-
though the platinum satellites are inherently broader
P
P
SnCl3
( 1 )
PhCN
PhCN
Cl
Cl
Cl
Cl
SnCl2
P
P
1b
Pt
Pt
Cl
P
P
1a
Pt
than the central lines, the J(31P, 195Pt) coupling con-
1
SnCl3
,
1b
stants of 2410 and 3740 Hz can be determined. These
diagnostic values refer to the trans and the cis arrange-
ment of the two phosphorus [3f,3g,3j], respectively, i.e.
trans-PtCl(SnCl3)(1) (1b) and cis-PtCl(SnCl3) (1) (1b0)
have been formed at a ratio of 60/40. The latter peak
shows further broadening upon cooling down to 238 K,
but unlike to the case observed with the tert-butyl ana-
logue of xantphos [8], no separation of the two signal (P
trans to chloro and P trans to trichlorostannato ligand)
has been observed.
P
P
2 K13CN
PPh3
P
P
N13
C
P
P
Ph P
3
P
Pt
Cl
Pt
Pt
Cl
13 CN
P
Cl
P
P
Cl
1c
1d
1e
Scheme 1. Synthesis of platinum(II)–xantphos complexes.
Table 1
NMR data of the platinum complexes of xantphos (1)a
dPA (ppm) dPB (ppm) 1J(195Pt, 31PA) (Hz)
1J(195Pt, 31PB) (Hz)
2J(PA, PB) (Hz) 2J(31P, 117=119Sn) (Hz)
b
b
1
cis-PtCl2(1) 1a
)16.8
7.1 (s)
15.5
–
–
3693
–
–
–
–
–
–
–
trans-PtCl(SnCl3)(1) 1b
cis-PtCl(SnCl3) (1) 1b0
trans-Pt(13CN)2(1) 1cf
trans-[PtCl(1)(PPh3)]Cl 1d
trans-[PtCl(1)(g1-1)]Cl 1eg
–
5.4d
2410 ꢀ 10
3740 ꢀ 25
2612
–
–
210 ꢀ 10c
e
5.4d
–
–
–
5.5 (t)
11.9 (t)
15.6 (t)
–
–
–
13.3 (d)
12.7 (d)
4141
4130
2593
2641
18.5
17.8
–
–
a Spectra were measured in CDCl3 (room temperature).
b PA and PB (phosphorus of double intensity) are assigned to PPh3 (or 1 as monodentate) and 1 (bidentate), respectively (multiplicities are given for
the central lines).
c Broad 117=119Sn satellites.
d PA and PB as one broad central line (close to coalescence at room temperature).
e
2
2
No detectable Jcis( (
117=119Sn, 31P) and Jtrans 117=119Sn, 31P) couplings.
f d(13C) ¼ 123.8 ppm (t); 1J(195Pt, 13C) ¼ 1074 Hz; 2J(31P, 13C) ¼ 14.1 Hz.
g dPC ¼ )22.1 ppm (noncoordinated phosphorus of 1).

1190
G. Pet€ocz et al. / Journal of Organometallic Chemistry 689 (2004) 1188–1193
The existence of a direct platinum–tin bond can be
conductivity of 68 molꢂ1 Xꢂ1 cm2 showing the partial
dissociation of one of the two chloro ligands, i.e. the
partial formation of a 1/1 electrolyte [Pt(1)(PPh3)
Cl]þClꢂ and not the neutral trigonal bipyramidal com-
plex PtCl2(1)(PPh3). Upon addition of one molar
equivalent of tin(II)chloride conductivity of 134.3
molꢂ1 Xꢂ1 cm2 has been measured due to the formation
of [Pt(1)(PPh3)Cl]þ[SnCl3]ꢂ.
By adding two molar equivalents of PPh3 to 1a,
equivalent conductivity of 94.8 molꢂ1 Xꢂ1 cm2 has been
obtained referring to a slightly higher dissociation than
in case of one equivalent of PPh3. In the presence of one
equivalent of tin(II)chloride even higher conductivity
(K0 ¼ 154:8 molꢂ1 Xꢂ1 cm2) was obtained due to nearly
quantitative formation of [Pt(1)(PPh3)Cl]þ[SnCl3]ꢂ (as
detected also by 31P NMR, vide supra) by facile disso-
ciation of the trichlorostannato leaving group.
It has to be added, that the natural bite angle of 111°
given for xantphos makes the cis-chelate coordination in
a square-planar geometry (ideal P–Pt–P bond: 90°) very
strained. On the other side, the two examples for trans-
chelation of xantphos known to date shows that the bite
angles of 153° [6a] and 150.7° [6b] are rather far from
(i.e. significantly smaller than) the ideal trans-coordi-
nation angle.
proved by NMR in case of 1b. The presence of cis tin
satellites in the 31P NMR spectra (2Jcis(117;119Sn, 31P) ꢁ
200 Hz) is a direct proof of the Pt–SnCl3 moiety. (As it is
well known, the 117Sn and 119Sn cis-satellites usually
coincide [9], so the tin satellites of about 8% intensity
can be determined even they are broad.) Unfortunately,
since the signals are close to coalescence, neither the
2
satellites due to Jcis(117;119Sn, 31P) nor those of
2Jtrans
( (
117Sn, 31P) < 2Jtrans 119Sn, 31P) cannot be assigned
in case of 1b0.
A complete cis/trans rearrangement occurred when
chloro–cyano ligand exchange reaction was carried out
by reacting 1a with two molar equivalent of K13CN
resulting in trans-Pt(13CN)2(1) (1c). Both the equiva-
lency of the two phosphorus (and consequently the two
cyano-carbons) and the magnitude of the coupling
1
2
constants (1J(195Pt, 31P); J(195Pt, 13C); J(13C, 31P)) re-
fer to the trans-chelation of 1.
Upon addition of PPh3 to the parent complex 1a the
formation of trans-[PtCl(1)(PPh3)]Cl ionic complex (1d)
takes place (Scheme 1). PPh3 occupies the position trans
to chloro ligand. A complex with similar square-planar
geometry has been obtained by reacting 1a with an ad-
ditional molar equivalent of 1. The entering ÔsecondÕ
xantphos ligand coordinates as a monodentate resulting
in [Pt(1)(g1-1)Cl]Cl (1e) (Table 1).
2.2. Hydroformylations
Coupling constants of diagnostic value for ÔPtP3Õ
species [10] can be observed also in case of 1d. The 31P
NMR spectrum consists of two patterns, a doublet and
a triplet (2Jcis(P,P) ¼ 18.5 Hz) at a ratio of 2/1 assigned
to the phosphorus of xantphos and PPh3, respectively.
Accordingly, the doublet and the triplet are flanked by
platinum satellites due to 1J(31P, 195Pt) couplings of
2593 and 4141 Hz, respectively. On the basis of 31P
NMR the xantphos (1) ligand might occupy either bis-
equatorial positions in a complex with trigonal bipyra-
midal geometry, with PPh3 at one of the apical
positions, or might coordinate as a trans-chelating li-
gand to form trans-[Pt(1)(PPh3)Cl]þ square-planar
complex cation. Both geometries would lead to an AX2
spin system in 31P NMR, although no preliminary
knowledge about the range of 1J(195Pt, 31P) coupling
constants in tbp structures is available. The two struc-
tures in solution can be distinguished by conductivity
measurements.
The possible formation of the ionic species under
similar conditions has been investigated with conduc-
tivity measurements. The neutral parent complex 1a has
been reacted with PPh3 both in the absence and in the
presence of tin(II)chloride in dichloromethane. On the
basis of previous results, the formation of a four-coor-
dinated complex cation [PtCl(1)(PPh3)]þ with chloride
and trichlorostannate counterion was expected, respec-
tively [10]. Accordingly, the addition of one equivalent
of PPh3 to the solution of 1a resulted in equivalent
Styrene (2) as the model substrate was reacted in the
presence of the platinum containing precursor 1a and
anhydrous tin(II)chloride with CO/H2 (1/1) at 25–100
°C and at a pressure of 120 bar (Table 2).
CO=H2
PhCH@CH2 ! PhCHðCHOÞCH3
2
3
þ PhCH2CH2CHO þ PhCH2CH3
ð1Þ
4
5
In addition to the formyl regio-isomers 3 and 4 also
the hydrogenation product 5 is expected to be formed as
usual under Ôoxo-conditionsÕ.
The tested platinum catalysts show catalytic activities
comparable to those published up till now. The plati-
num–xantphos system proved to be active in the above
temperature range. At lower temperatures (below 40 °C)
the activity is negligible and lower than usually ob-
served. The low activity of the system at room temper-
ature probably cannot be explained by the extremely
long induction period, since slightly increasing conver-
sions have been obtained in 50 and 116 h reaction time
at 25 °C. The conversions at higher temperature are in
the same range as usually expected. However, strikingly
different features related to the previous platinum-based
systems has been observed.
1. The platinum–xantphos catalyst differs from all the
previous ones in providing complete chemoselectivity
toward aldehyde regioisomers. The hydrogenated

G. Pet€ocz et al. / Journal of Organometallic Chemistry 689 (2004) 1188–1193
1191
Table 2
Hydroformylation of styrene (2) with PtCl2(1) + 2SnCl2 catalytic systema
b
c
Entry
Temperature (°C)
Reaction time (h)
Conversion (%)
RC (%)
Rlin (%)
1
25
40
50
50
28
24
24
24
2
25
76
70
89
91
>99.8
>99.8
>99.8
>99.8
>99.5
99
79
84
87
87
88
87
2
3
60
80
4
5d
80
100
6
a Reaction conditions (unless otherwise stated): 30 ml toluene, 0.1 mol styrene (2); p(CO) ¼ p(H2) ¼ 40 bar; Pt/2 ¼ 1/4000.
b Selectivity towards formyl products [(mol 3 + mol 4)/(mol 3 + mol 4 + mol 5) ꢃ 100].
c Selectivity towards linear regioisomer [(mol 4/(mol 3 + mol 4) ꢃ 100].
d p(CO) ¼ 40 bar; p(H2) ¼ 80 bar.
side-product, 5 has not been detected even in traces at
low temperatures. (The reaction can be considered as
chemospecific except for the data obtained at around
100 °C.) This high chemoselectivity is exceptional
even in rhodium-catalysed hydroformylations. It is
worth noting that aldehydes were formed exclusively
even at higher hydrogen partial pressure (p(CO) ¼ 40
bar; p(H2) ¼ 80 bar).
good leaving SnCl3 ligand forms a counter-ion provid-
ing a vacant coordination site in four-coordinated spe-
cies [12].
For cis-chelating ligands an optimum of natural bite
angle has been obtained concerning catalytic activity:
the hydroformylation activity increases with increasing
natural bite angle, however for larger bite angles it drops
[14]. It has been shown, that the larger the bite angle of
the ligand, the higher the ratio of complexes containing
the ligand as a trans-chelating one. The activity of the
catalyst decreases accordingly [8]. The explanation is
based on the facts, that both carbon monoxide insertion
and hydrogenolysis is slowed down in case of square-
planar platinum complexes with trans-chelating ligands,
since trans/cis isomerization has to occur. The cis-co-
ordination of the phosphorus donors is considered as a
prerequisite of migratory insertions [15].
In our case however, neither the decrease in catalytic
activity, nor that of the chemoselectivity has been ob-
served. In contrary, unexpectedly high hydroformylation
selectivity and regio-selectivity towards linear aldehyde
have been obtained. If 1 is coordinated as a trans-che-
lating ligand in square-planar catalytic species, the drop
in activity would be expected as a consequence of the
trans disposition of alkene and hydrido ligand (plati-
num-alkyl intermediate formation step) or carbonyl and
alkyl ligand (platinum-acyl intermediate formation
step).
2. The regio-selectivity towards linear aldehyde (4) is
much higher than in any other cases by using plati-
num–phosphine–tin(II)halide systems for styrene
hydroformylation. The regio-selectivity of hydro-
formylation is sensitive to the variation of the temper-
ature. While at room temperature branched
selectivity of about 20% has been obtained, it is
dropped to almost 10% at 100 °C. (The tendency of
forming linear aldehyde (4) rather than branched
one (3) at higher temperatures is what expected.) It
has to be noted, that the predominant formation of
the linear aldehyde has been observed in the plati-
num-catalysed hydroformylation of 1-octene using
xantphos-type ligands [11]. In a related carbonylation
reaction, in palladium-catalysed hydroxycarbonyla-
tion, branched to linear ratio of 19/81 for the two car-
boxylic acid regioisomers (2-phenylpropionic acid vs.
3-phenylpropionic acid) was found [5b]. This regio-
selectivity is very close to those obtained in our hyd-
roformylation experiments (Table 2).
On the basis of the catalytic results, we suppose that 1
occupies diequatorial positions of the tbp geometry in
catalytically highly active species of low concentrations.
Assuming the apical coordination of the chloro(trichlo-
rostannato) ligand, the cis position of the hydrido-ligand
and the coordinated olefin, as well as the alkyl-ligand and
the coordinated CO necessary for insertions is ensured,
and facile insertion providing platinum-alkyl and plati-
num-acyl species could take place, respectively. The
importance of the formation of five-coordinated cata-
lytic species has been shown by a recent theoretical study
[16]. In case of a ligand like 1 with natural bite angle close
to the optimum of 120° in trigonal geometry, the coor-
dination in diequatorial positions of a tbp structure is
supposed (Fig. 1).
2.3. Mechanistic considerations
The generally accepted mechanism of platinum-ca-
talysed hydroformylation is based on the square-planar
catalytic intermediates [9,12]. The role of tin(II)halide
(in most cases tin(II)chloride) is crucial, but not fully
cleared up considering all steps of the catalytic cycle. It
can act as a SnClꢂ3 counter-ion, a Lewis acid and a tri-
chlorostannato-ligand bonded to platinum by forming a
Pt–Sn bond [9,12,13]. In case of generally used bidentate
ligands, coordinated in cis-manner exclusively, ionic
mechanism has been postulated for the CO activation
step, its insertion into the Pt-alkyl bond forming Pt-acyl
complexes and that of the product forming step. The

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G. Pet€ocz et al. / Journal of Organometallic Chemistry 689 (2004) 1188–1193
3.2. Synthesis of PtCl2(1) (1a)
H
H
H
H
H
H
H
H
H
H3P
H3P
P
P
Pt
A degassed solution of 46.7 mg (0.099 mmol) di-
benzonitrilo platinum(II)chloride in 6 ml benzene is
heated to 80 °C for about 5 min and a degassed solution
of 57.9 mg (0.1 mmol) xantphos is added under argon.
The reaction mixture is refluxed for 1 h and then stirred
at room temperature for another 16 h. The precipitated
product is washed with benzene and hexane and dried in
vacuum. Yield: 92%. Anal. Calc. for C39H32Cl2OP2Pt:
C: 55.51; H: 3.83. Found: C: 55.76 H: 3.95. For NMR
see Table 1.
Pt
Ph
SnCl3
SnCl3
Fig. 1. Pentacoordinated platinum(II) species (Pt–PH3 complex [16]
and the suggested structure for Pt–1–SnCl2 (P–P ¼ 1) complex).
The trend of increasing regio-selectivity towards lin-
ear aldehydes is also explained by the increasing natural
bite angle of the ligand, which leads to an increase of the
steric congestion and to the formation of less hindered
linear rhodium-alkyl (and acyl) intermediate [8,17].
It can be concluded that the high activity of plati-
num–1–tin(II)chloride systems and the unexpectedly
high chemoselectivity of the hydroformylation reaction
could be explained by two reasons: (1) A square-planar
complex precursor containing 1 can extend its coordi-
nation number to five in case of platinum-hydrido and
platinum-alkyl complexes and might easily activate
carbon monoxide without the dissociation of any ligand
(including trans activating SnClꢂ3 ). (2) The xantphos li-
gand (1) due to its large bite angle occupies diequatorial
and trichlorostannato ligand one of the apical positions.
Consequently, the cis arrangement of hydrido and
alkene ligands, as well as that of the alkyl and carbon
monoxide ligands in axial–equatorial disposition is
assured.
3.3. Synthesis of PtCl(SnCl3)(1) (mixture of cis and
trans isomers)
To the stirred solution of 186 mg of 1a (0.22 mmol) in
20 ml chloroform 41.8 mg of anhydrous SnCl2 (0.22
mmol) was added at room temperature. After 2 h stirring
a few drops of pentane was added to the cooled solution (0
°C) and the pale yellow solid was filtered. Yield: 78%.
Anal. Calc. for C39H32Cl4 OP2PtSn: C: 45.31; H: 3.12.
Found: C: 45.54 H: 3.30. For NMR see Table 1.
3.4. Synthesis of trans-Pt(1)(13CN)2 (1c)
The PtCl2(1) complex (1a) (84.5 mg; 0.1 mmol) was
added to the solution of potassium cyanide (13.2 mg; 0.2
mmol) dissolved in 15 ml methanol. The powder did not
dissolved but was kept in suspension at 50 °C with con-
stant stirring for 10 h. The white powder-like crystals were
filtered, washed with water, methanol and ether then
dried. Yield: 85%. Anal. Calc. for C39(13C)2H32N2OP2Pt:
C: 59.72; H: 3.90; N: 3.39; Found: C: 59.92; H: 4.11; N:
3.27. For NMR see Table 1.
3. Experimental
3.1. General procedures
All reactions were carried out under Ar using stan-
dard Schlenk techniques. Toluene was distilled from
sodium in the presence of benzophenone. Diethylether
and benzene were distilled from LiAlH4. Styrene was
freshly distilled before use.
NMR spectra were recorded in CDCl3 (if not other-
wise noted) on a Varian Inova 400 spectrometer at
400.13 MHz (1H), 100.62 MHz (13C) and 161.89 MHz
(31P). Chemical shifts d are reported in ppm relative to
CHCl3 (7.26 and 77.00 ppm for 1H and 13C, respec-
tively) or relative to H3PO4 (31P). In case of in situ
NMR experiments a similar procedure was followed as
described in 3.3–3.6 (at 10 lmol scale), but CDCl3 was
used as solvent).
3.5. Synthesis of [PtCl(1)(PPh3)]Cl (1d)
To the stirred solution of 148 mg (0.175 mmol) of 1a
in 10 ml chloroform 45.9 mg (0.175 mmol) of PPh3 was
added. After 2 h stirring the solvent was evaporated and
the residue crystallised from benzene/methanol (1/1)
mixture. Yield: 67%. Anal. Calc. for C57H47Cl2OP3Pt:
C: 61.89, H: 4.29; Found: C: 62.08; H: 4.43. For NMR
see Table 1.
3.6. Synthesis of [PtCl(1)(g1-1)]Cl (1e)
To the stirred solution of 125 mg of 1a (0.15 mmol) in
10 ml chloroform 85.6 mg (0.15 mmol) of 1 was added.
After 2 h stirring the solvent was evaporated and the
residue crystallised from benzene/methanol (1/1) mix-
ture. Yield: 72%. Anal. Calc. for C78H64Cl2O2P4Pt: C:
65.86; H: 4.54; Found: C: 65.97; H: 4.76. For NMR see
Table 1.
Elemental analyses were measured on a 1108 Carlo
Erba apparatus.
The catalytic precursor PtCl2(PhCN)2 was prepared
as described previously [18]. Samples of the catalytic
reactions were analysed with a Hewlett–Packard 5830A
gas chromatograph fitted with a capillary column coated
with OV-1.

G. Pet€ocz et al. / Journal of Organometallic Chemistry 689 (2004) 1188–1193
1193
3.7. Hydroformylation experiments with 1a
(e) G. Consiglio, F. Morandini, M. Scalone, P. Pino, J.
Organomet. Chem. 279 (1985) 193;
ꢀ
(f) L. Kollar, G. Consiglio, P. Pino, J. Organomet. Chem. 330
ꢀ
In a typical experiment a solution of 21.3 mg (0.025
mmol) of PtCl(SnCl3)(1) and 9.5 mg (0.05 mmol) of
SnCl2 in 30 ml toluene containing 0.1 mol of styrene is
transferred under argon into a 150 ml stainless steel
autoclave. The reaction vessel is pressurised to 80 bar
total pressure (CO/H2 ¼ 1/1) and the magnetically stir-
red mixture is heated in an oil bath. The pressure is
monitored throughout the reaction. After cooling and
venting of the autoclave, the pale yellow solution is
immediately analysed by GC.
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Acknowledgements
The authors thank the Hungarian National Science
Foundation for the financial support (OTKA T023525)
and Johnson Matthey for the loan of platinum chloride.
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